1. Technical Field
The present invention relates to the performance estimation and scale-up methods for the mixer of the so-called rotor-stator type, and more specifically to the mixer that includes a stator having a plurality of openings (holes) and a rotor that is disposed on the inner side of the stator and spaced by a predetermined gap away from the stator.
2. Background
As shown in FIG. 1, it is general that the mixer of the so-called rotor-stator type comprises a mixer unit 4 that includes a stator 2 having a plurality of openings (holes) 1 and a rotor 3 disposed on the inner side of the stator 2 and spaced by a particular gap δ from the stator 2. Such mixer of the rotor-stator type is provided for subjecting the fluid or liquid being processed to the emulsification, dispersion, particle size breakup, mixing or any other similar process, by taking advantage of the fact that a high shear stress may be produced in the neighborhood of the gap between the stator 3 capable of rotating at high-speeds and the stator 2 being fixed in position. This mixer may be used for mixing or preparing the fluid or liquid being processed, and has a wide variety of applications in which foods, pharmaceutical medicines, chemical products and the like can be manufactured.
The mixer of the rotor-stator type may be classed according to the type of the circulation mode for the fluid or liquid being processed, that is, one type being the externally circulated mixer in which the fluid or liquid being processed may be circulated in the direction indicated by the arrow 5a in FIG. 2, and the other type being the internally circulated mixer in which the fluid or liquid being processed may be circulated in the direction indicated by the arrow 5b in FIG. 2.
For the mixer of the rotor-stator type mentioned above, many different configurations and circulation modes or systems have been proposed. For example, the Japanese patent application No. 2006-506174 discloses the rotor and stator apparatus and method for forming the particle sizes, and proposes the particle size breakup apparatus and method for forming the particle sizes using the mixer which will be described below. Specifically, the mixer includes the stator having a plurality of openings (holes) and the rotor disposed on the inner side of the stator and spaced by a particular gap away from the stator, and can be used widely in the manufacturing fields, such as the pharmaceutical medicines, nutrition supplement foods, other foods, chemical products, cosmetics and the like. Using the apparatus and method described above, the mixer can be scaled up in the efficient, simple and easy manner.
For those past years, several indices (theories) have been reported as the performance estimation methods for the mixers having the different configurations.
Not only for the mixer of the rotor-stator type as described above but also for all other type mixers, it is reported that, when the liquid-to-liquid dispersion in particular is performed, for example, the drop diameter sizes can be discussed in terms of the magnitude of the values that can be obtained by calculating the average energy dissipation rate (Publications 1 and 2). In those publications 1 and 2, however, the method for calculating the average energy dissipation rates is not disclosed specifically.
The publications 3 to 6 report several study cases that may be applied to each individual mixer and in which the results obtained by making the experiments on those individual mixers have been arranged or organized into the graphical chart. In those study cases (Publications 3 to 6), however, it is considered that the mixer's particle size breakup effect is only affected by the particular gap between the rotor and stator and by the openings (holes) on the stator. It is only described that this differs for each different type mixer.
Several study cases are also reported (Publications 7 and 8), in which the particle size breakup mechanism for the mixer of the rotor-stator type was considered and discussed. In those publications 7 and 8, it is suggested that the energy dissipation rates of the turbulent flow will contribute to the particle size breakup effect for the liquid drop, and this particle size breakup effect may be affected by the frequency (shear frequency) of the turbulent flow when the fluid or liquid is placed under the shear stress of the fluid or liquid being processed.
For the scale-up method for the mixer of the rotor-stator type, there are several reports (Publication 9) in which the final resulting drop diameter (maximum stable diameter) can be obtained during the long-time mixer running period. This, however, is not practical in the actual production sites and is of no utility. Specifically, there are no reports regarding the study cases in which the processing (agitation and mixing) time of the mixer is the object for consideration, and those study cases are not useful enough to estimate the resulting drop diameters that can be obtained during the particular mixer running period. Although it is reported that the resulting drop diameters may be estimated by considering the mixer processing time, yet it is only reported that the phenomenon (factual action) is based on the actual measured values (experimental values). In those study cases, such phenomenon is not analyzed theoretically.
The following publication, which is the document related to the patent application, is cited herein for reference:                Japanese Patent Application No. 2005-506174        
The following publications, which are not related to the patent application, are cited herein for reference:    (1) David, J. T.; “Drop Sizes of Emulsions Related to Turbulent Energy Dissipation Rates”, Chem. Eng. Sci., 40, 839-842 (1985) and David J. T.; “A Physical Interpretation of Drop Sizes in Homogenizers;    (2) Davies, J. T.; “A Physical Interpretation of Drop Sizes in Homogenizers and Agitated Tanks, Including the Dispersion of Viscous Oils”, Chem. Eng. Sci., 42, 1671-1676 (1987);    (3) Calabrese, R. V., M. K. Francis, V. P. Mishra and S. Phongikaroon; “Measurement and Analysis of Drop Size in Batch Rotor-Stator Mixer”, Proc. 10th European Conference on Mixing, pp. 149-156, Delft, the Netherlands (2000);    (4) Calabrese, R. V., M. K. Francis, V. P. Mishra, G. A. Padron and S. Phongikaroon; “Fluid Dynamic and Emulsification in High Shear Mixers”, Proc. 3rd World Congress on Emulsion, pp. 1-10, Lyon, France (2002);    (5) Maa, Y. F., and C. Hsu, and C. Hsu; “Liquid-Liquid Emulsification by Rotor/Stator Homogenization”, J. Controlled. Release, 38, 219-228 (1996);    (6) Barailler, F., M. Heniche and P. A. Tanguy; “CFD Analysis of a Rotor-Stator Mixer with Viscous Fluids”, Chem. Eng. Sci., 61, 2888-2894 (2006);    (7) Utomo, A. T., M. Baker and A. W. Pacek; “Flow Pattern, Periodicity and Energy Dissipation in a Batch Rotor-Stator Mixer”, Chem. Eng. Res. Des., 86, 1397-1409 (2008);    (8) Porcelli, J.; “The Science of Rotor-Stator Mixers”, Food Process, 63, 60-66 (2002);    (9) Urban, K.: “Rotor-Stator and Disc System for Emulsification Processes”, Chem. Eng. Technol., 29, 24-31 (2006)